Possible role of carpal hyperextension in superficial digital flexor tendinopathy.

REASONS FOR PERFORMING STUDY: The specific biomechanical circumstances that induce excessive superficial digital flexor tendon (SDFT) strain in horses are unknown. HYPOTHESIS: Carpal joint hyperextension during axial limb loading during the middle of stance disproportionately enhances SDFT strains compared to suspensory ligament (SL) strains. METHODS: Superficial digital flexor tendon and SL strains were measured in 7 cadaver limbs during in vitro loading that maintained carpal extension or allowed carpal hyperextension by constraining, or allowing rotation of, the radius during loading conditions that simulated the middle of stance at the walk. The effect of carpal hyperextension on SDFT and SL strains and joint angles was assessed using repeated measures ANOVA. RESULTS: Limb loading generally resulted in higher SL strains than SDFT strains for both carpal extension and hyperextension loading conditions. Compared to carpal extension, carpal hyperextension resulted in increased strains in both the SDFT and the SL; however, a greater increase in strain was seen in the SDFT. On average, carpal hyperextension caused approximately 3° greater carpal extension, 1° greater metacarpophalangeal joint hyperextension, 1° greater proximal interphalangeal joint flexion and <1° greater distal interphalangeal joint flexion than did carpal extension. CONCLUSIONS AND CLINICAL RELEVANCE: Carpal joint hyperextension is likely to induce disproportionately higher strain in the SDFT than in the SL. Factors that affect carpal stability are likely to affect the risk for superficial digital flexor tendinopathy.

The Visible Human Dataset: the anatomical platform for human simulation.

One goal of a medical school education is to teach the anatomy of the living human. With the exception of some surface anatomy, the morphology education that goes on during a surgical procedure, and patient observation, live human anatomy is most often taught by simulation. Medical anatomy courses utilize cadavers to approximate the live human. Case-based curricula simulate a patient and present symptoms, signs, and history to mimic reality for the future practitioner. Radiology has provided images of the morphology, function, and metabolism of living humans but with images foreign to most novice observers. With the Visible Human database, computer simulation of the live human body will provide revolutionary transformations in anatomical education.

The visible human male: a technical report.

The National Library of Medicine's Visible Human Male data set consists of digital magnetic resonance (MR), computed tomography (CT), and anatomic images derived from a single male cadaver. The data set is 15 gigabytes in size and is available from the National Library of Medicine under a no-cost license agreement. The history of the Visible Human Male cadaver and the methods and technology to produce the data set are described.

The Visible Human data set: an image resource for anatomical visualization.

The National Library of Medicine (NLM) has long been a world leader in the archiving and distribution of the print-based images of biology and medicine. NLM has also been a pioneer in the use of computer systems to encode and distribute textual knowledge of the life sciences. NLM's Long Range Planning effort of 1985-86 foresaw a coming era where NLM's bibliographic and factual database services would be complemented by libraries of digital images, distributed over high speed computer networks and by high capacity physical media. The NLM Planning Panel on Electronic Imaging recommended that NLM should undertake the building of a digital image library consisting of computer-assisted tomography (CAT), magnetic resonance interferometry (MRI), and cryosection images of a representative, carefully selected and prepared male and female cadaver--the "Visible Human Project." The male Visible Human data set is now being made available through a license agreement with the NLM. A wide range of educational, diagnostic, treatment planning, and commercial uses is predicted. The Visible Human data set and its associated identification maps will serve as a "Boston Teapot" for medical imaging, a common public domain data set against which all medical imaging algorithms can be tested, and a cornerstone for future sets of related image libraries.

Muscle performance and adenine-nucleotides status in MCA-sarcoma tumor-bearing rats.

The reduction in DNA, RNA, amino acid, and total protein in muscle tissue of tumor-bearing rats may influence muscle function. The effects of MCA-sarcoma tumor burden on muscle performance and adenine nucleotides was evaluated in three fiber types of skeletal muscle. Twenty-one days after MCA-sarcoma tumor inoculation, the gastrocnemius-soleus muscle group of Fischer 344 rats was stimulated using an in situ preparation; tetanic stimulation for 10 min at 7.5, 15, or 30 tetani per min (TPM) or 60 TPM for 5 min (n = 6 control and six tumor-bearing rats/group). ATP, ADP, AMP, IMP, phosphocreatine, and creatine content in white and red gastrocnemius muscle and soleus muscle was measured. There were no differences among controls and tumor-bearing rats in force output; however, ATP content in the soleus muscle of tumor-bearing rats was significantly reduced after 30 TPM for 10 min or 60 TPM for 5 min. The performance of skeletal muscle, over a wide range of stimulation frequency, in tumor-bearing rats does not appear to be influenced by changes in adenine nucleotide content.

Adenine nucleotide degradation in slow-twitch red muscle.

The catabolism of adenine nucleotides (AdN) in rat soleus muscle (predominantly slow twitch) is very different from that in fast-twitch muscle. AMP deaminase is highly inhibited during brief (3 min) intense (120 tetani/min) in situ stimulation, resulting in little inosine 5'-monophosphate (IMP) accumulation (0.21 mumol/g). Even with ligation of the femoral artery during the same brief intense contraction conditions there is surprisingly little increase in IMP (0.37 mumol/g), although AdN depletion is evident (-1.30 mumol/g). We have tested the hypothesis that accumulation of purine nucleosides and bases accounts for the AdN depletion by measuring purine degradation products using high-performance liquid chromatography. There was no stoichiometric accumulation of purine degradation products to account for the observed AdN depletion even though metabolite recovery was essentially quantitative. We hypothesis that under these conditions AdN are converted to a form different from purine nucleoside and base degradation products. In contrast to the inhibition of AMP deamination seen during brief ischemia, slow-twitch muscle depletes a substantial fraction (28%) of muscle AdN (1.75 mumol/g) that can be accounted for stoichiometrically as purine degradation products during an extended 10-min ischemic period of mild (12 tetani/min) contraction conditions. IMP accumulation (1 mumol/g) is most prominent with inosine, accounting for 23% (0.4 mumol/g) of the depleted AdN, showing that slow-twitch red muscle is capable of both AMP deamination and the subsequent production of purine nucleosides during an extended period of ischemic contractions. The present results indicate that AdN metabolism in the soleus muscle is complex, yielding expected degradation products or a loss of total purines, depending on contraction conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

ATP depletion in slow-twitch red muscle of rat.

Rat slow-twitch muscle, in contrast to fast-twitch muscle, maintains its ATP content near normal during intense stimulation conditions that produce rapid fatigue. An extensive depletion of adenine nucleotide content by the deamination of AMP to IMP + NH3, typical of fast-twitch muscle, does not occur. We evaluated whether this response of slow-twitch muscle could be simply due to failure of synaptic transmission or related to cellular conditions influencing enzyme activity. Stimulation of soleus muscles in situ via the nerve or directly in the presence of curare at 120 tetani/min for 3 min resulted in extensive fatigue but normal ATP contents. Thus the lack of ATP depletion must be related to cellular events distal to neuromuscular transmission. Even nerve and direct muscle stimulation (with curare) during ischemia did not cause a large depletion of ATP or a large elevation of lactate content (12.0 +/- 0.7 mumol/g), even though the decline in tension was essentially complete. However, if the same tension decline during ischemia was prolonged by stimulating for 10 min at 12 tetani/min a large decrease in ATP (2.24 +/- 0.09 mumol/g) and increase in IMP (2.47 +/- 0.16 mumol/g) and lactate (30.4 +/- 2.0 mumol/g) content occurred. Thus adenine nucleotide deamination to IMP can occur in slow-twitch muscle during specific contraction conditions. The cellular events leading to the activation of AMP deaminase require an intense contraction condition and may be related to acidosis caused by a high lactate content.

Response of plasma beta-endorphins to transcutaneous electrical nerve stimulation in healthy subjects.

A study of 31 healthy volunteers was done to test the hypothesis that analgesia produced by low frequency/high intensity (LoF/Hil) transcutaneous electrical nerve stimulation (TENS) is mediated by release of beta-endorphin (beta-E). After randomization, Group 1 (n = 10) received no stimulation (placebo); Group 2 (n = 9) received 30 minutes of high frequency/low intensity (HiF/Lol) TENS; and Group 3 (n = 12) received 30 minutes of low frequency/high density (LoF/Hil) TENS. Blood pressure, pulse, plasma beta-E levels, and evoked potential response were measured before and after treatment. Mean plasma beta-E increased with treatment in Groups 2 and 3 and fell in Group 1, but the difference between the groups was not statistically significant. Sixty-seven percent of Groups 2 and 3 showed an increase in plasma beta-E levels compared with 30 percent in Group 1 (two-sample test of proportions, p less than .05). Evoked potential response, a measure of pain threshold, varied directly with plasma beta-E level independent of the type of treatment applied. This study did not demonstrate a difference between the effects of HiF/Lol versus Lof/Hil TENS on plasma beta-E in healthy subjects.

Axoplasmic transport in the toad Bufo marinus.

The rate and course of axoplasmic transport from the eighth dorsal root ganglion cell bodies into the sciatic nerve of the toad Bufo marinus were studied. Concentrated tritiated proline was hydraulically injected into a surgically exposed dorsal root ganglion of animals maintained at 19 +/- 0.5 degrees C. At postinjection intervals of 1, 6, and 10 h, the animals were sacrificed and the dorsal root, ganglion, and sciatic nerve were removed bilaterally. The dorsal roots and peripheral nerves were cut into 3 mm segments measured from the ganglion. In some experiments all tissues were prepared for liquid scintillation counting techniques. In others the ganglion and every fifth 3 mm nerve segment were fixed in Bouin's fixative for radioautography, and the remaining tissue segments were prepared for liquid scintillation counting methods. Scintillation counts (counts/min) of consecutive segments along the labeled nerve were plotted against distance (mm) for each animal. Examination of these profiles showed a peak of radioactivity in the injected ganglion for each animal that was followed distally by an abrupt drop in the adjacent segments of the nerve. Radioactivity remained relatively stable in subsequent segments forming a plateau and then dropped to baseline levels forming a wavefront in the distal portion of the peripheral nerves of the 6 and 10 h toads. Movement of this wavefront during the 6 to 10 h time interval provided evidence for an axoplasmic flow rate of about 120 mm/day. Radioautographs of the ganglion and representative segments along the sciatic nerve were examined with both bright- and dark-field microscopy. Accumulations of silver grains were observed overlying the injected ganglion cell bodies and labeled axons of the nerve. Values for the number of silver grains/unit area were obtained from dark-field radioautographs of the nerve segments through the use of a computer-microscope system. The relative amount of radioactivity present in the axons was thereby demonstrated. Radioautographic data confirmed the axoplasmic flow rate of about 120 mm/day determined by liquid scintillation counting methods for the bulk of radioactive materials transported at this fast rate. In addition, the evaluation of radioautographic data suggests that an even faster flow rate of 185-215 mm/day may exist for a small portion of the labeled materials transported in the axon.

The two-course system in gross anatomy.

In response to the continuing pressures facing anatomy and other basic sciences in medical education, the Department of Anatomy at the University of Colorado School of Medicine has instituted a parallel two-course system of teaching gross anatomy. Students in both the longer and shorter of the two courses appear to be prepared adequately by their experiences in the courses they elected. Statistically significant differences (students in the longer course scoring higher) were, however, observed on both departmental examinations and certain national examinations administered subsequent to the completion of the courses. Student responses to both courses were extremely favorable. Since the differences between the two groups were generally small and advantages were noted in presenting two courses simultaneously, it is concluded that the concurrent presentation of two differently organized basic science courses (within a single subject area) offers an effective response to the instructional needs of our medical school and medical students.